Among crawler tracks, there are those in which cores are embedded at a uniform pitch in the longitudinal direction of the crawler track, and so-called coreless crawler tracks in which cores are not embedded at all. The rigidity of the latter as a crawler track overall is substantially uniform, and therefore, the latter is mounted to a relatively high speed vehicle and used for traveling.
Further, with regard to the transmitting of drive force to such a coreless crawler track, rubber projections are formed at a uniform pitch at the inner peripheral surface of the crawler track, and on the other hand, sprockets are provided at the drive shafts of the vehicle, and the sprocket teeth engage with the rubber projections and transmit drive force. Further, usually, flange portions are fixed to the left and the right of the peripheral edge of the sprocket, and these flange portions are structured so as to rotate while contacting the left and right inner peripheral surfaces of the projections of the crawler track.
FIG. 1 is a cross-sectional view showing the relationship between such a crawler track and a sprocket, and FIG. 2 is a side view thereof. In the figures, 10 is a coreless crawler track, and rubber projections 11 are formed at a uniform pitch at the inner peripheral side thereof, and rubber lugs 12 are formed at the outer peripheral side. Such lugs 12 travel while contacting a road surface.
Reference numeral 20 is a sprocket, and teeth (here, pins) 21 stand erect at the peripheral edge thereof at the same pitch as the aforementioned rubber projections 11, and further, flange portions 22 are provided at the left and right of the peripheral edge. The pins 21 engage with the rubber projections 11, and the flange portions 22 contact the inner peripheral surface of the crawler track and transmit drive force.
Moreover, soil and sand A entering into an inner peripheral surface 10a of the crawler track 10 while traveling cannot be avoided, and the phenomenon in which this accumulates at the inner peripheral surface arises. FIG. 3 is a cross-sectional view showing this state, and FIG. 4 is a side view thereof. When such a phenomenon arises, the positional relationship between the crawler track 10 and the sprocket 20 becomes offset from the expected state. Therefore, what is particularly affected is the rubber projections 11, and because drive force is applied while the pins 21 are offset from the proper meshing positions, great strain arises at the rubber projections 11, and there have been cases in which they have been damaged.